Emma’s Rainbow Dash look is inspired by Rainbow Dash, a character from the My Little Pony franchise and one of the main characters in My Little Pony: Friendship is Magic who appears in Equestria Girls! Rainbow Dash’s human version possesses long, rainbow colored hair with bangs hanging in the right side of her face. Her clothing consists of a blue short-sleeved button up shirt and a white shirt with her pony version’s cutie mark logo on the chest. Her lower half consists of tight-fitting black bike shorts underneath a pink and white skirt, rainbow colored knee socks, and light blue Converse style high top boots. For accessories, she wears rainbow colored wristbands. The human version of Rainbow Dash is the captain of every sports team in Canterlot High. She was once friends with the human versions of Applejack, Pinkie Pie, Fluttershy, and Rarity before Twilight Sparkle’s arrival. However, one time she and the softball team were asked by Applejack to perform at a bake sale. Sunset Shimmer tricked Rainbow into coming on the wrong day by sending her a phone message saying that the bake sale was postponed, with the message being addressed from Applejack. This misunderstanding made Rainbow feel abandoned, and she and Applejack ignored each other thereafter. They later got back together. Rainbow Dash helps Twilight after seeing she has heart for not giving up when they played soccer. When Twilight invokes the power of the element of magic, Rainbow gains pony ears and wings. After Sunset Shimmer is defeated, Rainbow flies around at the dance, picking up the human Scootaloo and giving her a ride. When the portal to Equestria closes after Twilight’s departure, Rainbow Dash’s wings and pony ears vanish.
Source: equestriagirls.wikia.com/wiki/Rainbow_Dash